Vaccines: Modern Trolley Car Dilemmas

BY MARK MCQUAIN

The Trolley Car dilemma is back in bioethics news. For those unfamiliar with the trolley car dilemma, you alone are responsible to operate a trolley track switch to divert an out-of-control trolley car away from five workers on one section of track only to cause the death of a lone worker on the only alternate section of track. The dilemma: someone is going to die, and you get to decide who. In a recent editorial in the June 13th New England Journal of Medicine, Dr. Lisa Rosenbaum nicely describes the utilitarian dilemma surrounding the public health risks and benefits associated with a vaccine for the dengue virus, a mosquito-borne virus that annually causes significant severe illness and death worldwide. The dengue vaccine, Dengvaxia, is a real-world trolley car dilemma. Dengvaxia presently can protect large numbers of patients from this deadly virus, but at the expense of causing severe illness and death in a much smaller number of patients, mostly children.

Dr. Rosenbaum describes our response to utilitarian thinking, correctly I think. We don’t mind utilitarian rules that negatively affect others, particularly when the rules tend to confer benefit to our group as a whole (the very definition of utilitarianism) but we resist utilitarian thinking when it threatens to affect us negatively as an individual despite overall benefit to the rest of our group. Healthy self-interest often conflicts with the utilitarian calculus that purports to determine the overall benefit to the group. In the case of Dengvaxia, if the deaths caused by the vaccine only occurred in people who would have died from the natural dengue virus anyway, there would be no problem. In other words, by golly, you all were going to die from the widespread disease anyway, and since the vaccine did save some of you from dying, there is really no new or additional loss. Net positive outcome, right?

Sadly, vaccines do not work that way. With Dengvaxia, it may be possible to create a pre-vaccine test for seropositivity for the virus. This would mean determining whether a person previously had a very mild case of the virus such that they would not suffer a catastrophic outcome from receiving the vaccine, thereby allowing them to safely receive the vaccine to prevent a more severe case of dengue in the future. Such a screening test may be possible but it would cost some unknown amount of additional money and would still not be 100% accurate. Even so, no vaccine is 100% safe.

How many lives would need to be saved and at what cost before we are satisfied with the cost/benefit ratio of Dengvaxia (or any vaccine for that matter)? Presently the World Health Organization is recommending a pre-vaccination test be developed and only vaccinate those who test positive for prior exposure. This is effectively saying that the vaccination is not only not required but not even presently recommended in endemic regions, this despite the fact that Dengvaxia clearly significantly reduces overall mortality and morbidity. If the disease were more contagious and more lethal than dengue, at what point does the vaccine, however imperfect, become mandatory? This is the ultimate trolley car switch for public health officials.

Aren’t trolley car dilemmas fun?

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